The present invention relates generally to fluid compressors, and more particularly, to an improvement in refrigerant compressors of the wobble type in which pistons are reciprocated by a wobble plate driven by a cam rotor which is secured to a drive shaft.
A wobble type compressor of this type is described in U.S. Pat. No. Re. 27,844 to Olson, which is incorporated herein by reference. In such a compressor, a wedge-shaped cam rotor is secured at the inner end of a drive shaft and is sandwiched between a wobble plate and front end plate, which rotatably supports the drive shaft. The wobble plate is connected to the pistons through connecting rods, is pivotally supported, and is prevented from rotating by suitable means. Therefore, the wobble plate can undergo oscillating or nutating movement following the rotation of the cam rotor, and the pistons slide within their cylinders. The wobble type compressor is small in size and is suitable for refrigeration systems in automobiles.
In the conventional refrigerant compressor, a charge of refrigerant gas and lubricating oil is maintained in the system. The refrigerant gas is compressed by a plurality of pistons which axially reciprocate within a corresponding plurality of cylinders. The reciprocal movement of the piston is, in turn, produced by the cooperation of the rotating cam rotor and the rotating wobble plate, which convert the rotation of the drive shaft to the desired reciprocal movement of the pistons. The compressed refrigerant gas together with the lubricating oil is forced out of the compressor to the refrigerant system and a quantity of lubricating oil is separated from the suction gas and passed into the compressor to lubricate desired components of the compressor.
It is desirable in the operation of such compressor that the amount of lubricating oil circulating in the compressor be proportional to the compressor operating speed. Moreover, it is generally desirable to utilize a minimum amount of lubricating oil and to minimize, if not prevent, the discharge of lubricating oil from the compressor to the refrigerant system. Reduction of the discharge of oil increases the operating efficiency of the condensor and evaporator, which are parts of the refrigerant system.
One recent attempt to improve the lubrication of a refrigerant compressor and minimize the discharge of lubricating oil therefrom is described in U.S. Pat. No. 4,005,948 to Hiraga, which is incorporated herein by reference. This patent discloses a lubricating system including a deflector projecting from the inner wall of the compressor housing which collects the lubricating oil splashed onto the housing wall and channels the lubricating oil thus collected to the shaft seal cavity. Therefore, the lubricating oil in a crank chamber is agitated by the movement of the cam rotor or the wobble plate and lubricates the internal moving parts in the form of an oil mist. A portion of the oil which flows along the inner surface of the compressor housing is collected by the deflector and flows into the shaft seal cavity to lubricate the shaft seal assembly.
In this construction, the discharge of lubricating oil can be reduced. However, generally a compressor is provided with a passageway or a balance hole to communicate the crank chamber with the suction chamber. This balance hole is provided to return the refrigerant "blow-by" gas in the crank chamber, which is leaked from the cylinders to the crank chamber through the gap between the inner surface of the cylinder and the piston, to the suction chamber. A portion of the lubricating oil is thus discharged through the balance hole to the suction chamber together with the returned blow-by gas. In particular, if the compressor is driven at high speed, the amount of blow-by gas leaked to the crank chamber is increased, and the velocity of flow in the balance hole is increased. The amount of discharged oil together with the refrigerant gas is, therefore, increased.
The prior art compressors thus require a relatively large amount of lubricating oil, which reduces the efficiency of operation of the refrigerant system of which the compressor is a part, while still not ensuring a sufficient amount of lubricating oil at all times during compressor operation. The known refrigerant compressors of the type described are thus subject to failure and reduced operating efficiencies.